Method of test for surface softening of natural building stones by exposure to acidic atmospheres
1967 Edition

Overview of the Standard's Coverage

Scope:

• Defines test methods relevant to assessing natural stone materials, aligning with national and international standards.
• Applicable to preparation and evaluation of stone samples shaped as prisms or cubes.

Essential Test Sample Parameters

Reporting Guidelines (Clause 6.2)

• Identification of sample including quarry name and location
• Details of ledge name or position
• Date of sample collection
• Trade name or grade of stone
• Size and shape of specimen
• Description of specimen preparation method

Visual Flowchart: Sample Preparation & Testing Process

flowchart TD
    A[Collect Sample] --> B[Prepare Specimen]
    B --> C[Grind Surface (IS Grit No. 80)]
    C --> D[Scrape Using Specified Tool (7.5x2 cm blade)]
    D --> E[Conduct Test and Document Findings]
    E --> F[Include Report Details: Quarry, Sampling Date, Grade, Specimen Info]

This structure ensures harmonized testing procedures compliant with the standard.

Sampling and Selection Requirements per IS 4122

Main Provisions:

• Clause 2.1: The sample selected must truly represent the average characteristics of the stone type or grade.
• Clause 2.2: The purchaser or authorized agent selects the sample directly from quarried stone or natural rock; the sample size must be sufficient to prepare the required test specimens.
• Clause 2.3: When noticeable differences in quality exist, multiple samples should be collected to capture the range of properties.

Specimen Identification Details (Clause 6.2):

• Quarry name and geographic location
• Ledge identifier or position
• Date of sampling
• Stone trade name or grade
• Specimen dimensions and shape
• Description of specimen preparation

Practical Considerations:

• Sampling must encompass quality variability to ensure representativeness.
• Adequate sample size is necessary to perform multiple tests such as compressive strength and water absorption.
• Maintaining accurate records supports traceability and quality control.

flowchart LR
    A[Quarried Stone or Natural Rock] --> B[Sample Selection by Authorized Person]
    B --> C{Is Quality Variable?}
    C -- Yes --> D[Collect Multiple Samples]
    C -- No --> E[Select Single Representative Sample]
    D & E --> F[Specimen Preparation]
    F --> G[Testing and Reporting]

For specimen sizes and preparation details, consult the IS 1121 series on stone testing.

Specifications and Preparation of Test Specimens per IS 4122

Specimen Size and Shape (Clause 3.1)

• Prismatic specimens: 10 cm wide × 10 cm deep × 20 cm long
• Cubic specimens: 10 cm edges
• Surfaces must be smoothly ground using an abrasive corresponding to IS Grit No. 80 (IS:715-1966), then cleaned thoroughly.

Number of Specimens Needed (Clause 5.1)

• At least three specimens should be tested for each evaluation.

Preparation Method (Clause 5.1)

• One face is scraped at its center point, located by the intersection of diagonals.
• Scraping depth (da) is calculated as the difference between thickness before and after scraping, measured with ±0.02 mm accuracy.
• Test is conducted at ambient temperature between 20 and 30°C.

Reporting Data (Clause 6.2)

• Sample identification including quarry and location
• Ledge name or position
• Sampling date
• Stone trade name or grade
• Specimen size and shape
• Method used for preparation

Summary Table: Specimen Dimensions and Preparation

flowchart TD
    A[Sample Collection] --> B[Specimen Formation]
    B --> C{Specimen Shape}
    C -->|Prism| D[10×10×20 cm]
    C -->|Cube| E[10×10×10 cm]
    D & E --> F[Surface Grinding with IS Grit No. 80]
    F --> G[Scrape Center of One Face]
    G --> H[Measure Thickness Before and After]
    H --> I[Compute Scraping Depth (da)]
    I --> J[Conduct Testing]

This protocol guarantees consistency and reliability for stone softening evaluation.

Hand Scraping Tool Requirements and Usage per IS 4122

Tool Dimensions (Clause 4.1)

• Blade length: 7.5 cm
• Blade width: 2 cm
• Blade tip: Flattened surface perpendicular to blade length, with sharp edges on both sides
• Material: Steel grade T-90 V23 as specified in IS:1570-1961

Scraping Method (Clause 5.1.1)

• Apply approximately 1.5 kg force on the cutting edge
• Hold blade at a 30° angle relative to the specimen surface
• Stroke length: about 4 cm forward
• Perform 8 scraping strokes per cutting edge, repeated on both sides (total 16 strokes per specimen)
• Sharpen the blade before testing each specimen

Sample Preparation Recap (Clauses 5.1 & 3.1)

• Specimens are prisms (10×10×20 cm) or cubes (10 cm edges)
• Surfaces are ground smooth with IS Grit No. 80 abrasive (IS:715-1966)
• Minimum of 3 samples are tested
• Scraping performed at center of one face, located by diagonals
• Ambient temperature during testing: 20 to 30°C

Measurement

• Scraping depth (da) is calculated as: [ d_a = t_{before} - t_{after} ] where thickness is measured to nearest 0.02 mm before and after scraping

flowchart LR
    A[Prepare Specimen] --> B[Grind Surface Smoothly]
    B --> C[Sharpen Scraping Tool]
    C --> D[Apply 1.5 kg Pressure at 30° Angle]
    D --> E[Perform 8 Scraping Strokes on One Edge]
    E --> F[Repeat 8 Strokes on Opposite Edge]
    F --> G[Measure Thickness Before and After]
    G --> H[Calculate Scraping Depth]

This summary covers essential tool characteristics, the scraping procedure, and measurement requirements.

Overview of the Testing Process per IS 4122

1. Specimen Preparation (Clause 5.1):

• Use at least three specimens per test.
• Perform scraping at the center of one face, found by intersecting diagonals.
• Calculate scraping depth (dₐ) as the difference between thickness before and after scraping, with a precision of ±0.02 mm.
• Conduct scraping in room temperature conditions (20°C to 30°C).

2. Scraping Tool Specifications (Clause 4.1):

• Blade dimensions: length of 7.5 cm, width of 2 cm.
• Blade edges are sharpened and perpendicular to blade length on both sides.
• Material: Steel T-90 V23 compliant with IS:1570-1961.

3. Reporting Details (Clause 6.2):

• Include sample ID, quarry location, and ledge position.
• Indicate the sampling date.
• Provide trade name or grade of stone.
• Mention specimen size and shape.
• Describe specimen preparation methodology.

4. Rounding Instructions (Clause 0.5):

• Final values should be rounded according to IS:2-1960 standards.

Summary Table of Scraping Tool Dimensions

flowchart TD
    A[Collect Sample] --> B[Prepare Specimen]
    B --> C[Scrape Center of Face]
    C --> D[Measure Thickness Before and After]
    D --> E[Calculate Scraping Depth (dₐ)]
    E --> F[Conduct Testing]
    F --> G[Record and Report Results]

This ensures a standardized and dependable process for evaluating stone surface softening.

Computation and Reporting Guidelines per IS 4122

Essential Equations:

• Softening Depth (d): [ d = d_2 - d_1 ] where:

  • (d_1) is the initial scraping depth before exposure
  • (d_2) is the scraping depth after acidic atmosphere exposure

• Mean Softening Depth: [ \bar{d} = \frac{\sum d_i}{n} ] where (n) is the number of specimens tested

• Rounding: Final values must be rounded in accordance with IS 2-1960.

Reporting Obligations (Clause 6.2):

• Identification of sample, including quarry name and location
• Ledge name or position
• Sampling date
• Stone trade name or grade
• Specimen dimensions and shape
• Description of preparation method

Reporting Precision:

• Softening depth should be reported to the nearest 0.02 mm.

Reporting Summary Table

flowchart TD
    A[Collect Sample] --> B[Prepare Specimen]
    B --> C[Measure Initial Thickness (d₁)]
    C --> D[Conduct Test Exposure]
    D --> E[Measure Final Thickness (d₂)]
    E --> F[Calculate Softening Depth (d₂ - d₁)]
    F --> G[Calculate Average Depth]
    G --> H[Document Test Results]

This methodology ensures clear, traceable, and standardized reporting for stone durability assessments.